(1) Field of the Invention
This invention relates to a combustor of a gas turbine comprising, in combination, film cooling means, pin fin cooling means and impingement cooling means for cooling wall surfaces of a combustor.
(2) Description of the Prior Art
To cope with a high temperature during operation, the combustor of a gas turbine has hitherto been provided with cooling means for cooling its wall surfaces.
It has hitherto been usual practice for the combustor to be provided with one of the film cooling means, pin fin cooling means and impingement cooling means or all or two of them in combination.
Japanese Patent Laid-Open No. 13015/77 discloses one example of cooling means comprising the aforesaid cooling means in combination, for example.
Of these three cooling means, the film cooling means forms a thin layer of cooling air in film form along the inner surface of the combustor. This cooling means is capable of achieving higher cooling effects than the other two cooling means.
In the film cooling means disclosed in the prior art document referred to hereinabove, a wall plate constituting a shell of the combustor is split into a multiplicity of wall members located axially of the combustor and successively arranged such that portions of the adjacent wall members overlap each other to define a cooling air space therebetween. Cooling air is introduced into this space and allowed to flow along the inner wall surface after being released from the space.
In the combustor provided with this film cooling means, the construction of the combustor is complex because the multiplicity of wall members are arranged to provide overlaps, so that fabrication of the combustor is difficult to perform and construction cost is high. An added disadvantage is that the combustor as a whole leaves something to be desired in strength.
In the combustor provided with the film cooling means of the aforesaid construction, the cooling air merely flows between the wall members, and difficulty has been experienced in cooling some particular surface portions of the wall plate. For example, an air inlet port is located at the wall plate of the combustor. When the film cooling means of the aforesaid construction is used, the cooling air does not flow in sufficiently large amounts to the wall surface portion disposed downstream of the air inlet port and such wall surface portion fails to be cooled sufficiently.